Abstract 4500: Exploring site-specific activation of kinase inhibitors via AKR1C3-mediated prodrug strategy

Targeted therapies such as kinase inhibitors have significantly advanced cancer treatment. However, targeting pan-essential kinases remains challenging due to the side effects associated with a narrow therapeutic window. To address this issue, we propose developing prodrugs that can be site-specifically activated by Aldo-keto reductase 1C3 (AKR1C3). Specifically, a kinase inhibitor prodrug will be selectively activated by AKR1C3 to release the active parent compound in tissues with overexpression of AKR1C3. In this study, we designed prodrugs of the kinase inhibitor OTS964, a potent inhibitor of the pan-essential kinase CDK11, modeled after the AKR1C3-activated prodrug OBI3424. Using rational design principles, our prodrugs were engineered for selective activation by AKR1C3. Enzymatic assays confirmed AKR1C3-mediated reduction of the prodrugs, liberating the parent compound OTS964. Subsequent in vitro assays demonstrated that these prodrugs retained comparable activity to the parent compound in cell viability, immunoblotting, and NanoBRET assays. This study introduces a promising strategy to enhance the therapeutic window of pan-essential kinase inhibitors by concentrating their effects in affected tissues while sparing normal cells. Citation Format: Esther Elonga, Zhengnian Li, Michael Martinez, Anuradha Tathireddy, Stephen M. Hinshaw, Nathanael S. Gray. Exploring site-specific activation of kinase inhibitors via AKR1C3-mediated prodrug strategy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4500.